As shown in FIG. 7, a film opening mechanism to be mounted in a film fitting device of the above-described type includes an artillery shell shaped mandrel 63 for causing an individual tubular film F to be opened into a predetermined shape by fitting it thereon, the individual tubular film F being formed by cutting a long film LF which is collapsed into a sheet which is supplied by means of a film supply roller unit 61 composed of a drive roller 61a and a follower roller 61b, into a predetermined length using a film cutting unit 62 having cutting blades 62a and 62b; and a film transport unit 64 for transporting the tubular film F fitted on the mandrel 63 toward a lower end of the mandrel 63. The film opening mechanism is configured to deliver the tubular film F which is opened into a predetermined shape which has been transported to a lower end portion of the mandrel 63 by means of the film transport unit 64 to a film fitting position α with predetermined timing by means of a film delivery unit 65 having a pair of shot rollers 65a and 65b which nip the tubular film F in cooperation with the mandrel 63 to fit the tubular film F onto a container B which has been transferred to the film fitting position α.
As shown in FIG. 8, higher position rollers 63a, middle position rollers 63b, lower position rollers 63c, and lower end rollers 63d are each rotatably attached to the mandrel 63 on side surfaces of a lower half portion of the mandrel 63 on an upstream side and a downstream side in a transfer direction of the container B in a state in which the circumferential surfaces project slightly, and concave portions 63e are formed to expose lower portions of the circumferential surfaces of the middle position rollers 63b. 
As shown in FIG. 7, the film transport unit 64 is composed of an upstream-side feed belt unit 64A and a downstream-side feed belt unit 64B respectively provided on the upstream side and the downstream side of the mandrel 63 in the transfer direction of the container B, which nip the tubular film F cut from the long film LF by means of the film cutting unit 62 in a state in which it is fitted on the mandrel 63, in cooperation with the mandrel 63 to thereby transport the tubular film F toward a lower side of the mandrel 63. The upstream-side feed belt unit 64A and the downstream-side feed belt unit 64B are each composed of a drive pulley 64a, four follower pulleys 64b, 64c, 64d, and 64e, and a feed belt 64f running around these pulleys.
The drive pulley 64a and the follower pulleys 64d and 64e are configured to nip the tubular film F in cooperation with the lower position roller 63c, the higher position roller 63a, and the middle position roller 63b of the mandrel 63 with the feed belt 64f interposed therebetween, and, as shown in FIG. 7, the follower pulley 64e is configured to support the mandrel 63 with the middle position roller 63b interposed therebetween as it enters the concave portion 63e formed in the mandrel 63.